This invention relates to the processing of photographic film.
More particularly, the invention relates to film processing apparatus.
When photographic film is printed, certain liquids are used which are capable of releasing noxious fumes. This is particularly true of the "wet gate" film printing method with reference to which the invention will hereinafter be described without, however, being limited thereto.
It is known to copy a "master" film by passing it through an apparatus in which each film frame is exposed in a film gate and--while so exposed--is photographed onto another film (the copy). Photographic emulsions are highly sensitive to physical damage and are therefore easily scratched. If there is a scratch on the master, this will be faithfully reproduced (photographically) on the copy which, needless to say, is undesirable. To overcome this problem, the socalled "wet gate printing" technique was developed.
In wet gate printing the master film passes through a film gate having two clear glass windows between which a liquid is entrapped. This liquid has a light refractive index which is the same as that of the film. It fills any scratches in the emulsion and makes them "invisible" to the camera which photographs the images of the master onto the copy film. Moreover, the presence of this liquid was found to confer additional benefits in terms of enhancing the quality of the copies made, for reasons known to those skilled in the art, and wet gate printing is now the industry-accepted manner of copying a master film.
The liquid used in wet gate printing is perchlorethylene, a fluid which, when it emerges into the atmosphere on the film coming out of the wet gate, turns into a noxious vapor. While the presence of these fumes is unpleasant in itself, there is now a suspicion that they may have a carcinogenic effect. This, of course, takes the matter out of the realm of being merely a nuisance and requires appropriate corrective action.